With the rapid development of semiconductor devices, the market competition is becoming more and more fierce, one of the main methods to prolong the service life of the products is to constantly reduce the area of the die. In the Mixed-Signal Circuit, the proportion of the capacitor area in the chip is considerable, thus manufacturing a capacitor having a high performance and high capacity is an inevitable trend of the development of the semiconductor device.
The capacitor in the semiconductor device can be divided into PIP capacitors (the upper and lower conductive plates are made of polysilicon, the intermediate layer is an insulator layer), MIM capacitors (the upper and lower conductive plates are made of metal, the intermediate layer is an insulator layer), and MIP capacitors (the upper conductive plate is made of metal, the lower conductive plate is made of polysilicon, the intermediate of layer is an insulator layer). As regarding to the PIP capacitor, after the lower conductive plate polysilicon is formed, in order to reduce the contact resistance of the device and improve the operating speed of the device, a metallic silicide (such as WSi) is usually formed on the lower conductive plate polysilicon, then an insulator layer (also known as the dielectric layer) is formed on the metallic silicide, and the upper plate polysilicon is formed on the insulator layer, thus the manufacture of the PIP capacitor is completed.
In the prior art, there are two methods for manufacturing PIP capacitor on the semiconductor device, which are as follows:
The first process includes the steps of: 1. forming the lower conductive plate polysilicon and the metallic silicide layer on the lower conductive plate polysilicon; 2. forming the source and the drain; 3. forming the insulator layer; 4. forming the upper plate polysilicon.
The second process includes the steps of: 1. forming the lower conductive plate polysilicon and the metallic silicide layer; 2. forming the insulator layer; 3. forming the upper plate polysilicon; 4. forming the source and the drain.
In the two processes, the capacitance of the PIP capacitor formed by the first process is generally small, the capacitance cannot be increased to 1.8 ff/m2 even though reducing the thickness of the insulator layer; the capacitance of the PIP capacitor formed by the second process can increased to 1.8 ff/m2, however, the PIP capacitor has a poor reliability.